Extreme flood could trap residents of proposed development, SES warns

The Kogarah Golf Club has been identified as a possible site for 500 new homes. Photo: Jane Dyson

The State Emergency Service (SES) has raised concerns about the proposed development of thousands of homes on a low-lying golf course in south Sydney, warning an extreme flood could leave residents stranded with no guarantee of rescue.

The NSW SES's concerns relate to the Kogarah Golf Club, located in the Cooks Cove northern precinct in Arncliffe, which the Department of Planning has identified as having the potential to hold up to 5000 new homes.

It is the same site where developer John Boyd Properties has outlined plans to build thousands of apartments, a sporting stadium, and cycling and pedestrian paths, which is predicated on a $100 million relocation of the Kogarah Golf Course to the southern precinct of Cook Cove.

In a submission to the Department of Planning's draft strategy for the Bayside West Precincts, Nicole Hogan, NSW SES assistant director of emergency management, said a flood assessment of a proposed development scenario on the golf course site was "deceptive" because it had not included the impact of a "probable maximum flood" in its analysis.

"To truly understand the flood risk in each precinct, the flood risk up to and including the probable maximum flood should be assessed," Ms Hogan submitted.

"It could be above these levels the consequences are most severe."

"To truly understand the flood risk in each precinct, the flood risk up to and including the probable maximum flood should be assessed."

Nicole Hogan, NSW SES assistant director of emergency management

The golf course is located on a low-lying parcel of land on the western bank of the Cooks River and to the north of the M5 east freeway.

Ms Hogan submitted the Department of Planning should be open to considering the proposed development was "not suitable for the location" if the flood risk was still considered "too high after mitigation strategies have been implemented or considered".

Responding to the comments, a spokesman for John Boyd Properties sought to assuage any concerns, saying the flood related matters raised by the SES were "not unusual for urban developments of this size".

He said the development team was currently preparing a planning proposal to rezone the Kogarah Golf Course for residential development, which would address "this and all other matters required by the Department of Planning."

The proposal will include "an assessment of the impacts from future development on the capacity or operation of existing local evacuation routes and an independent concept emergency response plan for floods up to the probable maximum flood level," the spokesman said.

According to the Department of Environment's Floodplain Development Manual, a "probable maximum flood" is the largest flood that "could physically occur at the location of interest". It is considered an "extremely rare event" and is used as a measure to assist emergency services in planning disaster responses.

The Cooks Cove Flood Impact Assessment, prepared by infrastructure consultancy firm AECOM for the Department of Planning's draft strategy, limited its analysis to the flood effects of a "once in a 100-year flood" on a proposed development scenario for the golf course.

However, the assessment referenced a separate 2009 study of the flood impact of the Cooks River, which found that a probable maximum flood would submerge the surrounding roads, potentially cutting off the existing evacuation routes.

AECOM's assessment concluded "during such an event it is likely that people on the site will be required to shelter in place".

Ms Hogan submitted that a "shelter in place" disaster response generally "presents a greater risk than a well-conducted evacuation," and should be used as a last-resort option.

As a "shelter in place" strategy could also increase risk to emergency service personnel, Ms Hogan said there could be "no guarantee that rescue will be available to residents who are effectively entrapped in a building during a flood".

One option for preventing this outcome would be to improve road access around the golf course site, she suggested.

A Department of Planning spokeswoman said AECOM's study was intended only as a "preliminary flood assessment" and would be supplemented by further detailed studies, including probable maximum flood considerations, once a planning proposal for the golf course was lodged by the developer.

The strategy for the Cooks Cove precinct "will be refined based on submissions received including the response from NSW State Emergency Services," the spokeswoman said.